1. Field Of The Invention
The invention relates generally to the vertical adjustment of a chair backrest relative to the chair seat such that the backrest can be manually raised or lowered to any of a plurality of selectable positions and releasably locked therein while being able to assume an angular attitude relative to the chair seat and responsive to a person's posture on the chair.
2. Background Objects And Summary Of The Invention
The present invention relates in general to devices which provide for the selective adjustment and positioning of structural components relative to one another. The device is, due to its inherent simplicity, highly suitable for adaptation to various height adjusting purposes.
Accordingly, an object of the present invention is to provide a known height adjusting device, such as is the subject of my U.S. Pat. No. 4,749,230, with hinges on two sides in such a fashion that the hinges can be incorporated with modifications to the existing height adjusting device in a highly economical manner.
The advantages of the device are numerous and it is also an object of this invention to provide for a more fully "ergonomic" seating device. It is also an object to provide a device which is capable of causing the chair backrest to more adequately conform itself to a person's seating habits reducing fatigue and improving task efficiency. The device is particularly useful on chairs equipped with tilting backs; as nOw the backrest can maintain adequate back lumbar support as the person tilts back.
In summary, a chair can be readily equipped with the invention for example by designing a hinge such that one "male" member is a metal extrusion and one "female" member is molded in a self lubricated material or vice versa. One member, preferably the "female" member is made so as to be fixedly engagable and received within apertures or notches symmetrically disposed on the sides of the track plate of the known height adjusting device. The other "male" member is made to be received and rotatably engaged by the "female" member and it is fixed onto the chair backrest. Thus the backrest can be made to change angular position or inclination relative to the chair "back-upright" responsive to a person's seating posture or back contour, while being also able to change height in accordance with the features of the known device.